A Swiss forensic team has found that Palestinian leader Yasser Arafat was poisoned to death in 2004 with radioactive polonium.

A team of experts, including from Lausanne University Hospital's Institute of Radiation Physics, opened Arafat's grave in the West Bank city of Ramallah last November, and took samples from his body to seek evidence of alleged poisoning.

According to Qatar-based Al-Jazeera, the Swiss team discovered levels of polonium at least 18 times higher than normal in Arafat's ribs, pelvis and in the soil that absorbed his remains.

"This has confirmed all our doubts," said Suha Arafat, who met members of the Swiss forensic team in Geneva on Tuesday. "It is scientifically proved that he didn't die a natural death and we have scientific proof that this man was killed."

She did not accuse any country or person, and acknowledged that the historic leader of the Palestine Liberation Organization had many enemies.

The Israeli government, however, dismissed the Swiss report, saying that the "findings are not conclusive."

"Even if they did find traces of polonium that could indicate poisoning, there's no evidence of how that poisoning occurred," The Guardian quoted Palmor as saying. "Before the Palestinian Authority jumps to conclusions, there are many questions still to be answered."

"Israel is not involved in any way," he said. "There's no way the Palestinians can stick this on us. It's unreasonable and unsupported by facts. We will see yet another round of accusations, but there's no proof."

The Guardian also quoted Dov Weissglass, who is a former aide to Ariel Sharon, the prime minister at the time of Arafat's death. Weissglass denied any Israeli involvement in the death of the Palestinian leader.

Professor David Barclay, a British forensic scientist retained by Al Jazeera to interpret the results of the Swiss tests, said the findings from Arafat's body confirmed last year's results from traces of bodily fluids on his underwear, toothbrush and clothing.

"In my opinion, it is absolutely certain that the cause of his illness was polonium poisoning," Barclay told Reuters. "The levels present in him are sufficient to have caused death.

"What we have got is the smoking gun - the thing that caused his illness and was given to him with malice."

The Swiss scientists' report, posted in full on Al Jazeera's website, was more cautious. It concluded: "Taking into account the analytical limitations aforementioned, mostly time lapse since death and the nature and quality of the specimens, the results moderately support the proposition that the death was the consequence of poisoning with polonium-210."

The same radioactive substance was slipped into a cup of tea in a London hotel to kill defecting Russian spy Alexander Litvinenko in 2006. From his deathbed, Litvinenko accused Russian President Vladimir Putin of ordering his murder.The British government refused to hold a public inquiry into his death after ministers withheld some material which could have shed light on Russia's suspected involvement.

Barclay said the type of polonium discovered in Arafat's body must have been manufactured in a nuclear reactor.

While many countries could have been the source, someone in Arafat's immediate entourage must have slipped a miniscule dose of the deadly isotope probably as a powder into his drink, food, eye drops or toothpaste, he said.

Arafat signed the 1993 Oslo interim peace accords with Israel and led a subsequent uprising after the failure of talks in 2000 on a comprehensive agreement.

Allegations of foul play surfaced immediately. Arafat had foes among his own people, but many Palestinians pointed the finger at Israel, which had besieged him in his Ramallah headquarters for the final two and a half years of his life.

The Israeli government has denied any role in his death, noting that he was 75 years old and had an unhealthy lifestyle.

An investigation by Al Jazeera television news channel first reported last year that traces of polonium-210 were found on personal effects of Arafat given to his widow by the French military hospital where he died.

That led French prosecutors to open an investigation for suspected murder in August 2012 at the request of Suha Arafat. Forensic experts from Switzerland, Russia and France all took samples from his corpse for testing after the Palestinian Authority agreed to open his mausoleum.

The head of the Russian forensics institute, Vladimir Uiba, was quoted by the Interfax news agency last month as saying no trace of polonium had been found on the body specimens examined in Moscow, but his Federal Medico-Biological Agency later denied he had made any official comment on its findings.

The French pathologists have not reported their conclusions publicly, nor have their findings been shared with Suha Arafat's legal team. A spokeswoman for the French prosecutor's office said the investigating magistrates had received no expert reports so far.

One of her lawyers said the Swiss institute's report, commissioned by Al Jazeera, would be translated from English into French and handed over to the three magistrates in the Paris suburb of Nanterre who are investigating the case.

Arafat fell ill in October 2004, displaying symptoms of acute gastroenteritis with diarrhea and vomiting. At first Palestinian officials said he was suffering from influenza.

He was flown to Paris in a French government plane but fell into a coma shortly after his arrival at the Percy military hospital in the suburb of Clamart, where he died on Nov. 11.

The official cause of death was a massive stroke but French doctors said at the time they were unable to determine the origin of his illness. No autopsy was carried out.

Barclay said no one would have thought to look for polonium as a possible poison until the Litvinenko case, which occurred two years after Arafat's death.

Some experts have questioned whether Arafat could have died of polonium poisoning, pointing to a brief recovery during his illness that they said was not consistent with radioactive exposure. They also noted he did not lose all his hair. But Barclay said neither fact was inconsistent with the findings.

Since polonium loses 50 percent of its radioactivity every four months, the traces in Arafat's corpse would have faded so far as to have become untraceable if the tests had been conducted a couple of years later, the scientist said.

"A tiny amount of polonium the size of a flake of dandruff would be enough to kill 50 people if it was dissolved in water and they drank it," he added.

The Al Jazeera investigation was spearheaded by investigative journalist Clayton Swisher, a former U.S. Secret Service bodyguard who became friendly with Arafat and was suspicious of the manner of his death.

Hani al-Hassan, a former aide, said in 2003 that he had witnessed 13 assassination attempts on Arafat's life, dating back to his years on the run as PLO leader. Arafat claimed to have survived 40 attempts on his life.

Arafat narrowly escaped an Israeli air strike on his headquarters in Tunisia in 1985. He had just gone out jogging when the bombers attacked, killing 73 people.

He escaped another attempt on his life when Israeli warplanes came close to killing him during the 182 invasion of Beirut when they hit one of the buildings they suspected he was using as his headquarters but he was not there. In December 2001, Arafat was rushed to safety just before Israeli helicopters bombarded his compound in Ramallah with rockets.

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